AFAIK Nigeria doesn't ban Bitcoin but the central Bank on Nigeria could freeze your account if they detect the funds came from Bitcoin, high inflation rate, still a third world countries means not prosperous yet. That's why the trading volume of Nigeria can't be compared to first or second world countries, however there's an article said Nigeria become the top 2nd Bitcoin trading volume but keep in mind it's only on Paxful [1] not an entire exchanges.

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[1] https://www.theguardian.com/technology/2021/jul/31/out-of-control-and-rising-why-bitcoin-has-nigerias-government-in-a-panic